1. Field
The present invention relates generally to fifth wheel hitches for coupling trailers to tractor trucks, and, in particular, fifth wheel hitches having adjustable positions, and further, to slide rail assemblies for fifth wheel hitches having stop blocks.
2. Description of the Related Art
Fifth wheel hitches for towing a trailer behind a towing vehicle have long been known in the art. Examples of fifth wheel hitches include those disclosed in U.S. Pat. Nos. 4,721,323, 5,449,191, and 5,707,070.
Referring to FIGS. 1A through 1D, a fifth wheel hitch assembly 101 includes a support frame 150 for mounting hitch assembly 101 to towing vehicle 109, such as, for example, to a truck. Support frame includes a pair of base rails 102a, b that are bolted to the bed and/or frame of the truck 109. Hitch plate 130 is mounted to a pedestal 155 by means of a trunnion arrangement, or journal bearing, allowing for pivotal fore-and-aft movement of hitch plate 130. Hitch plate 130 includes a latch assembly (not shown) which further includes a jaw assembly specifically adapted to releasably engage and hold a kingpin 115 of a trailer 119 desired to be towed by the towing vehicle 120.
Some fifth wheel hitch assemblies 101 are adjustable axially with respect to the towing vehicle 109 frame. One way of achieving this feature is attach slide rails to the support frame of the hitch and configure the pedestal 155, upon which the hitch plate and latch assembly is mounted, to slidably engage the slide rails 151a, b. The conventional design of these slide rails is often a simple flange extending inward of the slide assembly which may be angled metal. Slide rails 151a, b are attached to the support frame by fillet welding and by bolts. Stop blocks are used to prevent over-travel of pedestal 155 in slide assembly and are affixed to the ends of slide rails 151a, b. 
Prior art stop blocks 105a-d are generally rectangular members that are affixed to the end of a slide plate usually with lap welding. A short-coming of this technique is that with such a small block there is a relatively small point of failure. Under large trailer loads, there can be excessive longitudinal forces pulling the hitch aft which may result in disassembly of the stop block from the fifth wheel slide assembly. Further, the attachment helping to support the stop block is limited to the slide plate area. Thus, a stop block is needed which will better withstand such longitudinal forces through distribution of the load.